KR20160144491A - Lithographic apparatus and device manufacturing method - Google Patents

Abstract

A lithographic apparatus is disclosed that includes a reflector (15) that deflects a beam of radiation, e.g., an EUV beam. The position of the reflector is controlled using a controller and positioning system. The positioning system includes a non-compensating actuator device 300 and a compensating actuator device 200 that compensates for the parasitic forces of the non-compensating actuator device. The positioning system and controller can provide a more accurate position of the reflector, reduce deformation of the reflector, and reduce the magnitude of the forces transmitted through the reflector.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lithographic apparatus,

This application is related to EP Patent Application 14165170.3, filed April 17, 2014, which is incorporated herein by reference in its entirety.

The present invention relates to a lithographic apparatus and a device manufacturing method. More particularly, the present invention relates to a system for controlling a reflector in a lithographic apparatus.

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, typically onto a target portion of the substrate. The lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). In that case, a patterning device, alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern may be transferred onto a target portion (e.g. comprising a portion of a die, a die, or several dies) on a substrate (e.g. a silicon wafer). The transfer of the pattern is typically performed through imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will comprise a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto a target portion at one time, and scanning the pattern through a beam of radiation in a given direction (the "scanning" direction) Called scanner, in which each target portion is irradiated by synchronously scanning the substrate in a direction parallel to the direction (parallel to the same direction) or in a reverse-parallel direction (parallel to the opposite direction).

In order to reduce the size of the features of the circuit pattern, it is necessary to reduce the wavelength of the imaging radiation. For this purpose, a lithographic apparatus using EUV radiation having a wavelength in the range of, for example, about 5 nm to 20 nm is under development. Since EUV radiation is heavily absorbed by almost all materials, optical systems and masks must be reflective, and the apparatus must be kept at low pressure or under vacuum. Any errors in directing the imaging radiation in the lithographic apparatus will have a greater impact on any errors, for example overlay errors, if the imaging radiation being used has a reduced wavelength, i.e. EUV.

Reflectors are used in the patterning means to locate the pattern image in the radiation beam. The image in the radiation beam is projected onto the substrate, which is very sensitive to the location of the image. Therefore, a greater accuracy of the position of objects, e.g., reflectors, in the lithographic apparatus may be desired to maintain overlay errors or any errors of the pattern in the radiation beam or, preferably, even to acceptable levels Is required. In general, any improvement in the accuracy of the control system that places the object will provide an advantage, since there are many objects that must be accurately located within the device, e.g., the lithographic apparatus.

It is therefore desirable to provide an improved system for controlling the position of reflectors and / or other components in a lithographic apparatus, particularly for devices that employ EUV radiation.

According to an embodiment of the present invention, there is provided a reflector comprising: a reflector; A positioning system N configured to position the reflector in N degrees of freedom is a positive integer, and the positioning system includes M actuator devices, each actuator device applying a force to the reflector Wherein M is a positive integer greater than N, at least one of the actuator devices is a compensating actuator device and at least one of the actuator devices is a non-compensating actuator device; And a controller configured to control the compensating actuator device and the non-compensating actuator device, the controller configured to control the compensating actuator device to compensate for parasitic forces of the non-compensating actuator device Compensating actuator device and non-compensating actuator device are configured to apply force to the object at the same point, and the controller is configured to control the compensating actuator device to compensate for parasitic forces of the non-compensating actuator device.

According to an aspect of the invention, there is provided an apparatus comprising a positioning system of the invention, the apparatus further comprising an object.

According to an aspect of the present invention, a method of compensating for vibration of an object using a positioning system of the present invention is provided.

According to an aspect of the invention, there is provided a device manufacturing method comprising projecting a projection beam of radiation onto a substrate positioned on a substrate table via a reflector, wherein the positioning system is arranged to position the reflector in N degrees of freedom Wherein the positioning system comprises M actuator devices, each actuator device is configured to apply a force to the reflector, M is a positive integer greater than N, and N is a positive integer, and wherein the positioning system comprises M actuator devices, At least one of which is a compensating actuator device and at least one of the actuator devices is a non-compensating actuator device; The controller is configured to control the compensating actuator device and the non-compensating actuator device, and the controller is configured to control the compensating actuator device to compensate for the parasitic forces of the non-compensating actuator device, wherein the compensating actuator device and the non- Wherein the controller is configured to control the compensating actuator device to compensate for parasitic forces of the non-compensating actuator device.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:
Figure 1 shows a lithographic apparatus used in an embodiment of the present invention;
Figure 2 is a more detailed view of the main optical path of the apparatus of Figure 1;
Figure 3a shows an actuator device used in a lithographic apparatus;
Figure 3B illustrates a compensating actuator device and a non-compensating actuator device in accordance with an embodiment of the present invention;
Figure 3c is a force diagram of forces applied to the reflector by the actuator devices of Figure 3b;
4 shows a representation of an actuator device;
5 is a detailed illustration of an actuator device used in an embodiment of the present invention;
Figure 6A shows forces acting on various points on a reflector in a lithographic apparatus;
FIG. 6B is a force diagram of the desired net forces of FIG. 6A; FIG. And
7 is a diagram illustrating forces at one point on a reflector in accordance with one embodiment of the present invention.

Figure 1 schematically depicts an EUV lithographic apparatus 4100 including a source collector apparatus SO. The apparatus comprises:

An illumination system (illuminator) (EIL) configured to condition a radiation beam EB (e.g., DUV radiation or EUV radiation);

A support structure (e.g., a mask table) (e.g., a mask table) coupled to a first positioner PM configured to support a patterning device (e.g., a mask or reticle) MA and configured to accurately position the patterning device MT);

A substrate table (e.g. a wafer table) (e.g. a wafer table) configured to hold a substrate (e.g. a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate WT); And

A projection system (e.g., a projection system) configured to project a pattern imparted to the radiation beam EB by a patterning device MA onto a target portion C (e.g. comprising one or more dies) For example, a reflective projection system (PS).

The support structure MT holds the patterning device. The support structure MT holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure MT may utilize mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device. The support structure MT may be, for example, a frame or a table, which may be fixed or movable as required. The support structure MT can ensure that the patterning device is in a desired position, for example with respect to the projection system. Any use of the terms "reticle" or "mask" herein may be considered synonymous with the more general term "patterning device".

The term "patterning device" should be broadly interpreted as referring to any device that can be used to impart a pattern to a cross-section of a radiation beam to create a pattern in a target portion of the substrate. The pattern imparted to the radiation beam may be precisely matched to the desired pattern in the target portion of the substrate, for example when the pattern comprises phase-shifting features or so-called assist features . Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in the device to be created in the target portion, such as an integrated circuit.

Examples of patterning devices include a mask and a programmable mirror array. Masks are well known in the lithographic arts and include mask types such as binary, alternating phase-shift and attenuated phase-shift, and various hybrid mask types. One example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam reflected by the mirror matrix.

The lithographic apparatus may be of a type having two or more substrate support structures, e.g., substrate stages or substrate tables, and / or a support structure for two or more patterning devices. In an apparatus having multiple substrate stages, all of the substrate stages may be uniform and interchangeable. In one embodiment, at least one of the plurality of substrate stages is specifically configured for exposure steps, and at least one of the plurality of substrate stages is specifically configured for measurement or preparation work steps. In one embodiment of the invention, at least one of the multiple substrate stages is replaced by a measurement stage. The measurement stage includes at least a portion of one or more sensor systems, such as a sensor detector and / or a target of the sensor system, and does not support the substrate. The measurement stage is positionable within the projection beam instead of the support structure or substrate stage for the patterning device. In such an apparatus, additional stages may be used in parallel, or preparatory steps may be carried out at one or more other stages while one or more stages are being used for exposure.

In an EUV lithographic apparatus, it is desirable to use a vacuum or low pressure environment, since gases can absorb too much radiation. Thus, a vacuum environment can be provided in the entire beam path with the aid of a vacuum wall and one or more vacuum pumps.

Referring to Figure 1, an EUV Illuminator (EIL) receives an extreme ultraviolet radiation beam from a source collector device SO. The source collector device SO is described in more detail below. Generally, a material (which may be referred to as a fuel) having at least one element with at least one emission line in the EUV range, such as xenon (Xe), lithium (Li) or tin (Sn) . This is accomplished by irradiating a droplet, stream, or cluster of fuel with a laser beam. The resulting plasma emits output radiation, e. G. EUV radiation, which is collected using a radiation collector disposed in the source collector device.

Different configurations of parts of the radiation system are possible. For example, where a CO ₂ laser is used to provide a laser beam for fuel excitation, the laser and source collector device may be separate entities. In this case, the laser is not considered to form a part of the lithographic apparatus, and the radiation beam can be emitted from the laser to the source collector, for example, with the aid of a beam delivery system comprising a suitable directing mirror and / or a beam expander. Device.

The EUV illuminator (EIL) may comprise an adjuster for adjusting the angular intensity distribution of the radiation beam EB. Generally, at least the outer and / or inner radial extent (commonly referred to as -outer and -inner, respectively) of the intensity distribution in the pupil plane of the illuminator can be adjusted. In addition, the EUV Illuminator (EIL) may include various other components, such as facetted field and pupil mirror devices. The EUV illuminator EIL can be used to condition the radiation beam EB to have a desired uniformity and intensity distribution in the cross section of the radiation beam EB.

The radiation beam EB is incident on a patterning device (e.g., mask) MA, which is held on a support structure (e.g., mask table) MT, and is patterned by a patterning device. After being reflected from the patterning device (e.g. mask) MA, the radiation beam EB passes through the projection system PS, which is directed onto a target portion C of the substrate W Focus. With the aid of the second positioner PW and the position sensor PS2 (e.g. interferometric device, linear encoder or capacitive sensor), the substrate table WT is moved, for example, along the path of the radiation beam EB To position different target portions C within the target portion C. Similarly, the first positioner PM and another position sensor PS1 may be used to accurately position the patterning device (e.g. mask) MA with respect to the path of the radiation beam EB . The patterning device (e.g. mask) MA and the substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks Pl, P2.

The depicted apparatus can be used in at least one of the following modes:

1. In step mode, the support structure MT and the substrate table WT are kept essentially stationary while the entire pattern imparted to the radiation beam is projected onto the target portion C at one time (i.e., Single static exposure]. The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged during a single static exposure.

2. In scan mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i. E., A single dynamic exposure )]. The speed and direction of the substrate table WT relative to the support structure MT may be determined by the magnification (image reduction) and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion during a single dynamic exposure, while the length of the scanning operation determines the height of the target portion (in the scanning direction).

3. In another mode, the support structure MT is kept essentially stationary holding a programmable patterning device, while the pattern imparted to the radiation beam is projected onto a target portion C while the substrate table WT Is moved or scanned. In this mode, a pulsed radiation source is generally employed, and the programmable patterning device is updated as needed after each movement of the substrate table WT, or between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography using a programmable patterning device, such as a programmable mirror array of a type as referred to above.

Combinations and / or variations on the above described modes of use, or entirely different modes of use, may also be employed.

A control system (not shown) controls the overall operation of the lithographic apparatus and, in particular, performs the optimization process described further below. The control system may be implemented as a suitably-programmed general purpose computer including a central processing unit and volatile and non-volatile storage. Optionally, the control system may further comprise one or more input and output devices, such as a keyboard and a screen, one or more network connections and / or one or more interfaces to various parts of the lithographic apparatus. It will be appreciated that a one-to-one relationship between the control computer and the lithographic apparatus is not required. In one embodiment of the invention, one computer can control multiple lithographic apparatuses. In one embodiment of the invention, a plurality of networked computers may be used to control one lithographic apparatus. The control system may also be configured to control the one or more associated process devices and the substrate handling devices in the lithocell or cluster in which the lithographic apparatus forms part. In addition, the control system may be configured to be subordinate to the supervisory control system of the lithocell or cluster and / or the entire control system of the fab.

Figure 2 shows EUV device 4100 in more detail, including a source collector device SO, an EUV illumination system (EIL), and a projection system PS. The source collector device SO is constructed and arranged such that a vacuum environment can be maintained in the surrounding structure 4220 of the source collector device SO. An EUV radiation emitting plasma 4210 may be formed by a discharge generating plasma source. EUV radiation may be produced by a gas or vapor, e.g., Xe gas, Li vapor, or Sn vapor, in which plasma 4210 is generated to emit radiation within the EUV range of the electromagnetic spectrum. Plasma 4210 is generated, for example, by an electrical discharge that causes a plasma that is at least partially ionized. For efficient generation of radiation, a partial pressure of, for example, 10 Pa of Xe, Li, Sn vapor or any other suitable gas or vapor may be required. In one embodiment, a plasma of tin (Sn) excited to produce EUV radiation is provided.

The radiation emitted by the plasma 4210 may be directed to an optional gas barrier and / or contaminant trap 4230 located in or after the opening of the source chamber 4211 In some cases, from a source chamber 4211 to a collector chamber 4212 via a contaminant barrier or a foil trap). The contaminant trap 4230 may comprise a channel structure. The contaminant trap 4230 can also include a gas barrier, or a combination of a gas barrier and a channel structure. In addition, the contaminant trap or contaminant barrier 4230 shown herein includes at least a channel structure known in the art.

Collector chamber 4212 may include a radiation collector (CO), which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 4251 and a downstream radiation collector side 4252. The radiation traversing the collector CO can be reflected by a grating spectral filter 4240 and focused on a virtual source point (IF). The virtual source point IF is typically referred to as intermediate focus and the source collector device is arranged such that the intermediate focus IF is located at or near the aperture 4221 in the surrounding structure 4220. [ The virtual source point IF is an image of the radiation emitting plasma 4210.

Subsequently, the radiation traverses the illumination system EIL, which provides a desired uniformity of the radiation intensity at the patterning device MA, as well as a desired uniform distribution of the radiation beam 421 at the patterning device MA, A faceted field mirror device 422 and a faceted pupil mirror device 424. Upon reflection of the radiation beam 421 at the patterning device MA held by the support structure MT a patterned beam 426 is formed and the patterned beam 426 is reflected by the projection system PS Is imaged onto the substrate W held by the substrate stage or substrate table WT via elements 428 and 430. [

In general, more elements may be present in the illumination optics unit IL and in the projection system PS than shown. The grating spectral filter 4240 may optionally be present depending on the type of lithographic apparatus. Also, there may be more mirrors than shown in the figures, for example, one to six additional reflective elements may be present in the projection system PS than that shown in FIG.

The collector optics (CO) as shown in FIG. 2 is shown as a nested collector with grazing incidence reflectors 4253, 4254, and 4255, but merely an example of a collector (or collector mirror) . Scratch incident reflectors 4253, 4254 and 4255 are axially symmetrically disposed about optical axis O and collector optics (CO) of this type are preferably combined with a discharge generating plasma source, often referred to as a DPP source Is used.

In the prior art, actuator devices are used to control the position of reflectors in the lithographic apparatus. Each actuator device is used to apply a control force to the reflector so that the reflector moves in a desired direction. Each actuator is configured to control the reflector in one degree of freedom. The actuator devices may include a field mirror device 422, a facet pupil mirror device 424, reflective elements 428 and 430, a patterning device MA, reflectors in the collector, such as intaglio reflectors 4253, 4254, And 4255) and / or any other mirror and / or reflector (not shown) in the lithographic apparatus. Any use of the term "mirror" herein may be considered synonymous with the more general term "reflector ".

A position controller is used by each actuator device to calculate the desired force to be applied to the object, e.g., the reflector. In the prior art, one actuator device is used to control the position of the reflector for each degree of freedom of the reflector to be controlled, i.e., a one-to-one relationship between the number of actuator devices and the degree of freedom of the controlled reflector exist. This relationship allows the position of the reflector to be fully controlled. The same number of actuators as the degrees of freedom are used in the prior art to avoid applying any stress to the reflector.

Because the accuracy of the reflector position effectively represents the level of accuracy required by the actuator devices of the present invention, as well as the advantages of precisely controlling components within the device, such as a lithographic apparatus, A reflector was used. The reflector may be interchanged with another object or component as will be described later in the present application.

The differences between the actual forces applied by the respective actuator devices as compared to the desired forces to be applied by the respective actuator devices can lead to an error in the direction of the reflected beam. Any component of force having a direction different from the direction of the desired force may be referred to as a parasitic force. The prior art actuators are controlled to avoid parasitic forces by adjusting the forces applied by the actuators.

Often, the force applied by the actuator device is not applied precisely exactly in the intended direction, which leads to parasitic forces. The term "parasitic force" is used to refer to unwanted forces and unwanted torques. The applied force discrepancies can be due to mounting tolerances, magnet variations and the position of the reflector. These discrepancies lead to parasitic forces acting on the reflector. The parasitic force is a force (and / or torque) that is not the intended direction, and thus the parasitic force is orthogonal to the intended direction.

Additionally, there are dynamic effects due to the oscillation modes of the actuators (as described in more detail below) that affect the control loop that controls the reflector position. The dynamic behavior of the actuator limits the bandwidth of the control loop. Hence, vibrations to different frequencies are detected and factored into the control loop by the controller in different ways.

Errors due to applied force mismatches can be avoided by limiting the number of degrees of freedom of each actuator by keeping the mechanical tolerances small in the prior art (e.g., by applying a translational force to the reflector in only one direction For example, by using a single actuator), and by limiting the stiffness of the connection between the reflector and the actuator, e.g., in the non-actuation direction.

The position controller can adjust the actuator to change the force applied to the reflector to account for some of the factors mentioned above. The position controller can determine the desired force at the other actuator devices to reduce or nullify the parasitic forces applied by the actuator device. Therefore, forces applied by the actuator devices at different points on the reflector can be used to compensate for parasitic forces in another actuator device. In this way, the forces applied to the reflector can be resolved to reduce the parasitic forces acting on the reflector. Ideally, the parasitic forces acting on the reflector will be zero so that the reflector will not move in any direction other than the desired direction.

However, in the prior art, there are problems because the prior art changes the forces applied by the actuators across the reflector, and these forces are transmitted through the reflector. These forces transmitted through the reflector result in deformations that occur in the reflector. Any deformations in the reflector-for example, deforming the shape of the reflector-can lead to errors. Errors in the position of the reflector, deformation of the reflector, and / or errors in the reflected radiation beam can lead to overlay errors, focus problems, and / or fading problems. In particular, overlay error can significantly affect the quality of the substrate being produced.

A simple model of an exemplary prior art positioning system is shown in Fig. 3A, which shows an actuator device 100 that applies a force Fn to a reflector 15. Fig. The figure shows one actuator device 100 (M = 1) that is controlled to position the reflector 15 at one degree of freedom (N = 1). In this example, the desired force is only in the z-direction. The position controller will be used to control the force applied by the actuator device 100 to reduce the difference in force, i.e., the applied force, as compared to the desired force. When multiple actuator devices are used, the controller may consider the forces applied by the other actuator devices.

As can be seen, the actual force Fn applied by the actuator device 100 has a force component Fpn in the x-direction as well as a force component F in the z-direction. The force component Fpn in the x-direction is a parasitic force, which is an unwanted force, which tends to induce an error in the position of the reflector 15.

The present invention solves the problems of the prior art described above. Embodiments of the present invention for solving these problems are described in more detail with reference to the drawings.

In the present invention, a lithographic apparatus is provided that includes a reflector and a positioning system configured to position the reflector in N degrees of freedom (where N is a positive integer). The positioning system includes M actuator devices (where M is a positive integer) and each actuator device is configured to apply a force to the reflector.

A controller is configured to control the actuator devices. In particular, the controller controls the compensating actuator device and the non-compensating actuator device, and the controller controls the compensating actuator device to compensate for the parasitic forces of the non-compensating actuator device.

A first embodiment of the present invention is shown in Fig. 3B. As shown in FIG. 3B, the positioning system is configured to position the reflector 15 at one degree of freedom (N = 1), i. E. In the z-direction. In this embodiment, two actuator devices (M = 2) are provided. In this embodiment, one of the actuator devices is a compensating actuator device 200, and the other actuator device is a non-compensating actuator device 300. The non-compensating actuator device 300 may be identical to the actuator device 100 shown in FIG. 3A, and / or may apply the same force. The non-compensating actuator device 300 applies a force Fn to the reflector 15 and the force Fn has a component in the z-direction which is the direction of the desired force and the component Fpn in the x-direction .

In this embodiment, N is the number of degrees of freedom. N non-compensating actuator devices are provided to control all degrees of freedom in this embodiment, and M-N compensating actuator devices are provided.

In an embodiment of the present invention, as shown in FIG. 3B, in addition to the non-compensating actuator device 300 (which is equivalent to the actuator device 100 shown in FIG. 3A), the compensating actuator device 200 is included. The compensating actuator device 200 applies a compensating force Fc to the reflector 15 and the force Fc has a component in the x-direction Frc and a component in the z-direction. In the present invention, a greater number of actuator devices are used than the degree of freedom being controlled, i. Using more actuator devices than the controlled degree of freedom can be referred to as "overactuation ".

3C shows a force diagram representing the force Fn applied by the non-compensating actuator device 300 and the force Fc applied by the compensating actuator device 200. FIG. The controller 50 controls the compensation actuator device 200 and the non-compensating actuator device 300 such that the compensating actuator device 200 is able to control the parasitic forces of the non-compensating actuator device 300 (Fpn in Figures 3a and 3b) As shown in FIG. The force diagram of Figure 3c shows how the forces applied by the actuator devices can be controlled to reduce parasitic forces (i.e., forces in the undesired direction, in this case the x-direction).

As shown in FIG. 3C, the components of the two forces in the x-direction cancel each other such that forces in the x-direction are in opposite directions and equal in magnitude. As such, the sum of these forces is zero. The forces applied by the compensating and non-compensating actuator devices may have a resulting force F in the z-direction. Compensating actuator device 200 and non-compensating actuator device 300 may be controlled to reduce or avoid parasitic forces (in this example, force in the x-direction).

In an embodiment of the present invention, compensating actuator device 200 and non-compensating actuator device 300 are configured to apply force to reflector 15 at the same point. Applying forces from different devices at the same point means that the forces can be resolved at the point of contact between the actuator devices and the reflector 15. [ Therefore, forces are dissipated at the contact rather than being transmitted through the reflector. In Figure 3B, forces are shown directly above the point of contact on the reflector 15 to more clearly indicate the forces.

The forces applied to the same point are such that multiple actuators have a very small contact area on the reflector so that each actuator device (at this point) is subjected to a force applied to the reflector by any adjacent actuator (s) ), Ideally as close as possible to one point on the reflector. In this way, multiple contact points from adjacent actuator devices can be applied to the "same point ". This has the same advantages as previously described in that the forces are disassembled at the same point so that they can not be transmitted to other different points through the mirror and can be localized or controlled according to the contact points configured with the reflector. Alternatively, forces applied at the same point may mean that the multiple actuators can be configured to contact the reflector at a single point of contact on the reflector. The compensating actuator device (s) and non-compensating actuator device (s) at the same point may be connected to each other before contacting the reflector, in order to apply force to a single point of contact rather than a plurality of closely spaced contact points. As such, the forces from the compensating actuator device (s) and the non-compensating actuator device (s) can be resolved relative to each other and the resolved force in a single direction at a single point of contact is applied to the reflector. This has the advantage that the stresses in the reflector are reduced because less force is dissipated in the reflector.

The actuator devices are controlled by a controller 50 configured to control the compensating actuator device 200 and the non-compensating actuator device 300. The controller 50 is configured to control the compensating actuator device 200 to compensate for the parasitic forces of the non-compensating actuator device 300. The controller 50 may control the compensating actuator device 200 and / or the non-compensating actuator device 300 to apply a linear force to the reflector 15 at the point of contact on the reflector 15. [ The controller 50 may control the compensating actuator device 200 and / or the non-compensating actuator device 300 to apply rotational force (i.e., torque) at the point of contact of the reflector 15.

The controller 50 may utilize the information provided by the at least one sensor. A sensor may be used to measure the movement and / or the position of the reflector 15. Information indicative of the movement and / or position of the reflector 15 may be transmitted from the sensor to the controller 50. The controller 50 determines the difference between the desired position of the reflector 15 in comparison to the actual (e.g., most recent) information of the reflector 15 by using a transfer function, for example, Can be used. The controller 50 may use the information received from the sensors and any existing or model-based stored information.

Controller 50 may utilize the aforementioned information to determine forces to be applied and controls compensating actuator device 200 and non-compensating actuator device 300 according to the calculated desired forces. Therefore, the controller 50 can adjust the forces applied by the actuator devices to reduce the error in the position of the reflector 15. [

One or more sensors may be used to provide the controller 50 with the necessary information. A sensor of the same type can be used to measure information for one reflector 15. Alternatively, different types of sensors may be used. For example, the sensor may be an interferometer, an encoder, a capacitive sensor, an eddy current sensor, or a position sensor in combination with an accelerometer of a velocity sensor. Preferably, the sensor is contact free.

The controller 50 of the present invention may be identical to a control system that controls the overall operation of the lithographic apparatus. Alternatively, the controller 50 of the present invention may be different from the control system that controls the overall operation of the lithographic apparatus.

The controller 50 will calibrate the actuator devices such that the forces applied by the actuator devices can be configured accordingly to reduce parasitic forces. Calibration can be done in several ways, for example using time or frequency domain calibration. The time domain calibration can be performed by switching off the actuator devices one by one. This calibration causes the forces applied by each actuator device to be determined. Alternatively, the relationship between the forces and the reflector 15 can be determined in the frequency domain by detecting a cross-talk between points at which force is applied to the reflector 15. Reducing the crosstalk of forces transmitted to the other points through the reflector 15 will reduce the parasitic forces on the reflector 15.

A simplified representation of the actuator device A is shown in Fig. In this embodiment, each of the actuator devices has an actuator 25 connected to the reflector 15 and the support frame 20. The connection between the actuator 25 and the reflector 15 may comprise a spring. The connection between the actuator 25 and the support frame 20 may include a spring. Any of the connections may include more than one spring, which are in series and / or parallel to one another. All connections may be made using at least one spring (as shown in FIG. 5).

Actuator device A may include actuator devices 100, 200, and 300 of FIGS. 3A and 3B, such as compensating actuator devices or non-compensating actuator devices, to be used for any of the aforementioned actuator devices . 4, the actuator 25 of the actuator device A applies a force F to the reflector 15. The overall connection between the reflector 15 and the support frame 20 is represented as a simple spring with a stiffness k. The actuator device of this embodiment is described in more detail with reference to Fig. 5, which includes a connection between an actuator 25 and a reflector 15 (reflector not shown) and a connection between an actuator 25 and a support frame 20 A detailed example of the actuator device A is shown. The actuator device A shown in Fig. 5 may be any of the aforementioned actuator devices, for example 100, 200 or 300.

5, the actuator device A is modeled as an actuator 25 connected to the support frame 20 and the actuator is connected to the reflector 15 by a weak spring connection to the reflector 15 and a weak spring connection to the support frame 20. [ Respectively. Two support arms 30a and 30b are attached to the support frame 20. The actuator is connected to the support arm 30a via two parallel springs 32a and 32b. The actuator is connected to the support arm 30b via two parallel springs 34a and 34b. The actuator is connected to the reflector 15 via two series springs 36a and 36b.

Each of the springs 32a, 32b, 34a, 34b, 36a and 36b has a predetermined stiffness. The stiffness of the springs is relatively low such that the connection between the support frame 20 and the actuator 25 and the connection between the actuator 25 and the reflector 15 are weak. It is advantageous for the vibrations on the support frame 20 to have weak connections so that they do not affect the reflector 15 and displacements of the reflector 15 relative to the support frame 20 do not induce large forces. The springs may have the same or different stiffnesses.

The dynamic relationship of the connection between the reflector 15 and the actuator is dominated by the springs 36a and 36b. There are different vibration modes in this connection due to the springs 36a and 36b. The lowest vibration modes are the bending modes at lower frequencies. The frequencies are low due to the low stiffness of the connections which must be kept low to reduce the parasitic forces when changing the position of the reflector 15. [ Alternatively, the connection acts as a shock absorber. The frequency of this mode can be adjusted so that the bandwidth requirement of the feedback control loop can be met. At higher frequencies, various modes occur, which limits the bandwidth of the controller 50 as a result.

The springs 32a, 32b, 34a, and 34b may be very rigid, in which case any reaction forces will be supplied from the actuator 25 to the support frame 20. When the springs 32a, 32b, 34a, and 34b are very rigid, the actuator 25 must compensate for the relatively large parasitic effects of high stiffness. Alternatively, when the springs 32a, 32b, 34a, and 34b are very weak, they act as mechanical filters of the reaction forces. Generally, it is advantageous to select the stiffness of the springs 32a, 32b, 34a, and 34b to be in a zone that does not have resonant modes that interfere with the controller bandwidth.

The different concepts are applicable to determine the optimal stiffness of 36a and 36b. In one example of an actuator used in the prior art, 36a and 36b are "very" rigid in the actuation direction and somewhat weak in the other direction. In this way, forces are efficiently transferred from the actuator to the reflector 15 in one direction. In this case, very stiffness means that the stiffness is high enough not to influence the total dynamic behavior of the control loop, but it is not too stiff enough to increase the parasitic stiffness significantly. There is an optimum ratio of the stiffnesses of the springs in different directions.

Although the same actuators can be used in the present invention, the selection of the stiffness of the springs is somewhat more liberal than in the prior art, since the increase in stiffness increases the parasitic forces, but the present invention does not compensate for the parasitic forces used to reduce these parasitic forces Actuator devices.

The dynamic effects of the actuator devices can be reduced by overwork. Therefore, the dynamic effects of the connection between the actuator and the frame 20 and the connection between the actuator and the reflector 15 can also be reduced. The effect of vibrations of the actuator due to the spring connections can be reduced so that the bandwidth of the controller 50 of the reflector 15 can be increased. This increases the control over the position of the reflector 15, which reduces the overlay error as described above.

The actuator 25 shown in Figure 5 is a Lorenz actuator with a coil assembly 5 and a magnetic assembly 10. The Lorentz actuator can be replaced by another type of actuator used in accordance with the present invention. In particular, other types of contactless actuators, such as reluctance actuators, may be used. Alternatively, a planar motor may be used to provide two actuators.

An advantage of the present invention is that the mechanical tolerances are less critical because the actuators are controlled to reduce the parasitic forces in accordance with the control loop. Therefore, the influence of mechanical errors in the lithographic apparatus is reduced because the force applied by the actuators will take into account these errors in determining the desired position of the reflector 15 and how much force is applied. Additionally, any reduction in errors in the system will improve the efficiency of the lithographic apparatus, meaning that the apparatus can produce substrates at a faster rate (correctly patterned). The present invention improves imaging quality. In addition, since the positioning system of the present invention takes into account any errors in the original position of the components in the apparatus, it is possible to use a positioning system to lead to a less complex assembly process, do.

Variations of this embodiment include a positioning system that controls the reflector 15 at a greater number of degrees of freedom-i. Thus, when the number of degrees of freedom controlled by the positioning system is increased, the number M of actuators must also be increased such that there is always at least one more actuator than the degree of freedom. Using a greater number of actuators and degrees of freedom makes the reflector 15 "over worked" in accordance with the present invention.

The number of actuators can be varied whether the number of degrees of freedom is changed or not. However, as mentioned above, the number of actuators M must be greater than the number of degrees of freedom N.

In the first embodiment, two actuator devices apply force to the reflector 15 at the same point. The number P of points at which force is applied to the reflector 15 can be varied.

In variants as in the previous embodiments or described, additional actuators may be included to apply a force to the reflector 15. Additional actuators may apply force to the same point on the reflector 15 as in the first embodiment. Alternatively, additional actuators may be used to apply force to different points on the reflector 15. Even if the additional non-compensating actuator device and / or the additional compensating actuator device apply forces at different points, overacting the reflector 15 (i.e., if M is greater than N) still provides advantages. The distance over which the forces are transmitted through the reflector 15 can be reduced compared to when the reflector 15 is not over-actuated. By overacting the reflector 15, the path of the forces through the reflector 15 can be controlled. In this way, it is possible to dissolve the forces through the reflector 15 in the desired zones and to avoid transmitting the forces through the reflector 15 in the other zones.

A second embodiment with a certain number of degrees of freedom N, actuator devices M, and points P at which the actuator devices apply force to the reflector 15 are illustrated.

Portions of the second embodiment that are identical or corresponding to those of the first embodiment are identified with the same references. Only the embodiments of the second embodiment which are different from the first embodiment are described below.

The second embodiment has a positioning system for controlling the reflector 15 in six degrees of freedom (N = 6). Nine actuators devices are used (M = 9), which applies a force to the reflector 15 at three separate points (P = 3).

For comparison, a top view of the prior art reflector 15 is shown in Fig. 6a, which has three points where forces are applied to the reflector 15. Fig. The points are labeled P1, P2 and P3. Figure 6a shows the forces applied by two actuators (not shown) at each point. (N = 6) and six actuator devices (M = 6) - i. E., The reflector 15) for the reflector 15 shown in Figure 6a There is one actuator device for each degree of freedom. If the same number of actuators as the number of degrees of freedom is used, the controller 50 can determine the forces required by the actuators to dissolve the parasitic forces within the reflector 15. One example of a prior art showing the forces of the actuators for the reflector 15 is shown in Fig. 6A, F1, F2 and F3 being the desired forces. Fp1 represents the parasitic force, that is, the unwanted force acting on the reflector 15. [

The controller 50 can be used to change the forces using Fr2 and Fr3 applied by the actuators at the second and third points, respectively, to dissolve the net forces on the reflector 15 so that the parasitic force is zero . However, in this example shown in Figure 6a, the parasitic forces are disassembled through the reflector 15. When the deformations of the reflector 15 are reflected from the reflector 15, it is possible to derive the angles of the radiation beam and the errors of the image in the radiation beam.

The desired forces of Figure 6a are shown in Figure 6b, which represent F1, F2 and F3 as mutually orthogonal forces. These represent three of the degrees of freedom that the positioning system is controlling. It should be noted that the orthogonal forces do not necessarily have to be coupled to the actuators which are arranged orthogonally. A decoupling matrix may be used for coordinate transformation of the forces applied by the actuators.

7 shows a plan view of a reflector according to a second embodiment of the invention in which forces at a first point are shown. In this embodiment, there is an additional compensation actuator device at each point. Thus, for example, at point P1, two non-compensating actuator devices (not shown) may apply a force to the reflector 15. The actuators will ideally be controlled by the controller 50 to apply F1. Any misalignments or discrepancies in force applied by the non-compensating actuator devices will result in a parasitic force modeled as Fp1 in FIG. A compensating actuator device (not shown) may be applied to the same point P1 to counteract the parasitic force Fp1 at this point.

By applying a force from the compensating actuator device at the same point as the non-compensating actuator devices, the forces can be resolved at P1 so that only the desired force F1 at this point acts on the reflector 15. [ Also, the points P2 and P3 have two non-compensating actuators and compensating actuators at each point, and can disassemble forces at those points, respectively.

Disassembling the forces at the individual points means that the parasitic forces are not dissipated through the reflector 15. Disassembling the forces at a particular point (or at several specific points) means that the parasitic forces are not transmitted through the reflector 15 and deformations in the reflector 15 can be reduced. This reduces any error in the position of the reflector 15 and any deformation of the reflector 15.

M and N may be any actual number of actuator devices and degrees of freedom, respectively, if M is greater than N. [ As shown in the previous embodiments, when the actuator devices at the same point are connected and apply a single force to the reflector at a single point of contact, or when the actuator devices apply forces from actuator devices adjacent to several contact points that are very close There is an advantage for M greater than N at the same point, regardless of whether the application is arranged to apply forces to the same point. Compensating actuator devices 200 apply force at the same point as the two non-compensating actuator devices, as in the previous embodiment with one point where N = 2 and M = 3, to provide.

The embodiments and figures show forces for clarity. They have been simplified to help explain the forces applied by the different actuators at different points on the reflector 15. [ For example, the forces shown in FIG. 3B may be at all degrees of freedom, but only in certain directions, for example in one plane. Force due to gravity on the reflector 15 is not included in the force diagrams or figures. The principles of the present invention can be applied to more complex systems. Also, in the figures, the ideal resultant forces are shown to completely dissipate the parasitic forces so that the parasitic forces are reduced to zero. One of the advantages of the present invention is that the parasitic forces can be reduced even if the forces are not fully decomposed.

The effect of gravity on the position of the reflector 15 may vary depending on the arrangement (i. E. Orientation) of the reflector 15, the positioning system and the controller 50 in the lithographic apparatus. The controller 50 will be able to take into account the influence of gravity by sensing the position of the reflector 15. Can be selectively controlled by the controller 50 to apply a force to the reflector 15 to override the force of gravity acting on the particular compensating actuator device 15 on the reflector 15. [

The terminology used to describe the actuator devices has been used for clarity. However, the terms "compensation" and "non-compensation" have been used to aid in the identification of the manner in which the actuator devices are being controlled, i.e. the compensating actuator device reduces parasitic forces applied by the at least one non-compensating actuator device It is used to apply force. The controller 50, which controls the compensating actuator device and the non-compensating actuator device, can control the devices to apply a specific force to the reflector 15. [ The devices may be exactly the same type of device, the devices may be the same size, and / or the devices may be interchangeable. In this specification, "interchangeable" means that the compensating actuator device can be controlled to apply the compensating force, but the controller can control the compensating actuator device to apply the non-compensating force, . This applies equally to non-compensating actuator devices in that the controller can change and control the device to apply a compensating force.

It may be advantageous to use different types of actuators to control one reflector 15. For example, it may be desirable to use a larger main actuator for realizing the main forces on the reflector 15, and smaller actuators configured to apply only a small force, for example, to reduce parasitic forces on the reflector 15 Can be advantageous. This may be advantageous in that less space is required than when all of the actuators are of the same size. Additionally, this may be beneficial to the dynamic behavior of the system. Using smaller and lighter actuators means that less weight is coupled to the reflector, leading to higher resonant frequencies, which may be an advantage. Alternatively, it is possible to apply forces of similar magnitudes to the reflector 15, i. E. To control the actuators so that the compensating actuator device 200 applies a force of magnitude similar to that of the non-compensating actuator device 300 to the reflector 15 Can be advantageous. As such, the forces may be applied by actuators of the same type and size, which may mean that the actuator devices are easier to source, replace, and / or repair.

The present invention may be used in combination with any optical elements used in a lithographic apparatus, laser and / or source collector, or more specifically any reflectors.

The diagrams and embodiments of the present invention are represented using an xyz coordinate system. This coordinate system was used for clarity. The angles of the actuator devices of the support frame 20, the reflector 15 and / or the positioning system may be varied. If desired, different coordinate systems may be used.

In the present invention, the term actuator device has been used to refer to a device that controls the position of a reflector at one degree of freedom. Multiple actuators can be combined in an actuator device, for example a planar motor actuator controlled by two degrees of freedom. Therefore, for a planar motor actuator, this will be considered as two actuators for the present invention. As such, the even number of actuators for the purposes of the present invention is equal to the number of degrees of freedom controlled by the actuator device.

According to the present invention, the positioning system and controller 50 as described in any of the preceding embodiments can be used to control the position of components of the lithographic apparatus other than the reflector. Examples of other components that may be controlled according to any of the preceding embodiments include components in an EUV or DUV device, e.g., measurement systems, a mask table, a substrate table, a laser, or a source collector, But is not limited to. The actuators can be actively damped on the component, or can be adapted to control, confine, or disperse vibrations in the device or the like.

The positioning system of any of the preceding embodiments can be used to control an object to damp vibrations of the object. Vibrations and / or oscillations of the object may be reduced by using a positioning system to compensate for movement of the object. This provides the advantages as described above for the previously described embodiments.

A method of manufacturing a substrate (W) according to the present invention includes projecting a projection beam through a reflector to pattern the substrate (W). The position of the reflector is controlled using the positioning system and controller 50 to reduce any errors of the patterned beam as it reaches the substrate W. [ The method of manufacturing the substrate may use a lithographic apparatus in any of the embodiments or variations as described above.

As will be appreciated, any of the features described above may be used with any other feature, as well as combinations thereof that are explicitly described in the present application.

Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, It should be understood that other applications may be made to manufacture components with microscale or even nanoscale features, such as the manufacture of displays (LCDs), thin film magnetic heads, and the like. In connection with this alternative application, any use of the terms "wafer" or "die" herein may be considered synonymous with the more general term "substrate" or "target portion", respectively. The substrate referred to herein can be processed before and after exposure, for example in a track (typically a tool that applies a resist layer to a substrate and develops the exposed resist), a metrology tool, and / or an inspection tool. Where applicable, the description herein may be applied to such substrate processing tools and other substrate processing tools. Also, for example, the substrate may be processed more than once to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that has already been treated multiple times.

While specific embodiments of the invention have been described above, it will be appreciated that the invention, which is a form of operation of the apparatus described at least here, may be practiced otherwise than as described. For example, embodiments of the present invention, at least in the form of a method of operation of the apparatus, may include one or more computer programs containing one or more sequences of machine-readable instructions describing how to operate the apparatus as described above, And may take the form of a data storage medium (e.g. semiconductor memory, magnetic or optical disk) in which the program is stored. In addition, the machine-readable instructions may be embodied in two or more computer programs. The two or more computer programs may be stored in one or more different memory and / or data storage media.

Any of the controllers described herein may operate in each case, or in combination, when one or more computer programs are read by one or more computer processors located within at least one component of the lithographic apparatus. The controllers may have any suitable configuration for receiving, processing and transmitting signals, either individually or in combination. One or more processors are configured to communicate with at least one of the controllers. For example, each controller may include one or more processors executing computer programs including machine-readable instructions for methods of operating the apparatus as described above. The controllers may include data storage media for storing such computer programs, and / or hardware for receiving such media. Thus, the controller (s) can operate in accordance with machine-readable instructions of one or more computer programs.

The above description is intended to be illustrative, not limiting. Accordingly, those skilled in the art will appreciate that modifications may be made to the invention as described without departing from the scope of the claims set forth below.

Claims (15)

A positioning system for positioning an object,
Wherein the positioning system is configured to position the object at N degrees of freedom and N is a positive integer, the positioning system comprising:
M actuator devices - each actuator device is configured to apply a force to a component, M is a positive integer greater than N, at least one of the actuator devices is a compensating actuator device, At least one of the actuator devices is a non-compensating actuator device; And
A controller configured to control a compensating actuator device and a non-compensating actuator device, the controller configured to control the compensating actuator device to compensate for parasitic forces of the non-compensating actuator device,
Wherein the compensating actuator device and the non-compensating actuator device are configured to apply force to the object at the same point on the object, and the controller controls the compensating actuator device to compensate for the parasitic forces of the non-compensating actuator device The location system comprising: The method according to claim 1,
Wherein the additional compensating actuator device and / or the additional non-compensating actuator device is configured to apply force to the same point, and wherein the controller is further configured to control the further compensating actuator device and / . 3. The method according to claim 1 or 2,
There are P points to which force is applied to the object, and P is a positive integer less than or equal to N. < RTI ID = 0.0 > The method of claim 3,
Wherein at the same point N is 2, M is 3, and there are two non-compensating actuator devices and one compensating actuator device. The method according to claim 3 or 4,
P is 3 position setting system. 6. The method according to any one of claims 1 to 5,
The controller controls the at least one compensating actuator device and the at least one non-compensating actuator device such that the net force applied at each point is orthogonal to the net force applied to any other point Positioning system configured. 7. The method according to any one of claims 1 to 6,
Wherein one of the M actuator devices comprises an actuator that is a Lorentz actuator or a reluctance actuator. 8. The method according to any one of claims 1 to 7,
Wherein the compensating actuator device and the non-compensating actuator device form an actuator that is a planar motor. 9. The method according to claim 7 or 8,
Wherein the actuator is connected to the object using at least one spring. 10. The method according to claim 8 or 9,
Wherein the actuator device is connected to the support frame using at least one spring. 11. The method according to any one of claims 1 to 10,
Wherein the force applied by the at least one actuator device is a linear force or a rotational force. 12. The method according to any one of claims 1 to 11,
Wherein the object is an optical element, more preferably a reflector. In a lithographic apparatus,
13. A lithographic apparatus comprising a positioning system according to any one of claims 1 to 12, wherein the lithographic apparatus further comprises the object, and wherein the object is a reflector. A method for compensating for vibrations of an object using a positioning system according to any one of claims 1 to 13. Projecting a projection beam of radiation onto a substrate positioned on a substrate table through an optical element,
Wherein the positioning system is configured to position the optical element at N degrees of freedom and N is a positive integer and wherein the positioning system includes M actuator devices each actuator device applying force to the optical element Wherein M is a positive integer greater than N, at least one of the actuator devices is a compensating actuator device, and at least one of the actuator devices is a non-compensating actuator device; Wherein the controller is configured to control a compensating actuator device and a non-compensating actuator device, the controller being configured to control the compensating actuator device to compensate for parasitic forces of the non-compensating actuator device, wherein the compensating actuator device and the non- Compensating actuator device is configured to apply force to the object at the same point on the object, and the controller is configured to control the compensating actuator device to compensate for parasitic forces of the non-compensating actuator device.

Images